JP7694052B2 - Organic EL display device and manufacturing method thereof - Google Patents

Description

The present invention relates to a technology that enables improved brightness in organic electroluminescence (EL) display devices.

Organic EL display devices are self-emitting display devices that use organic light-emitting diodes (OLEDs), and there are two known light-emitting methods. One is the RGB method, and the other is the color filter method.

In the RGB system, one pixel is formed by sub-pixels made of red (R), green (G), and blue (B) light-emitting diode elements. Since no color filters are used, the light-emitting efficiency is high and it is also possible to increase color purity.

The color filter method is a method of forming a color image by combining red (R), green (G), and blue (B) color filters with a white OLED. Since the light emission intensity of the white OLED element corresponding to each color can be controlled independently, it is possible to increase the color purity of dark areas (black) and also to display a high contrast.

Although the color filter method has the disadvantage of low light emission efficiency, it has the advantage of a simple manufacturing process, low cost, and favorable miniaturization. For this reason, in fields such as microdisplays and large TVs, the color filter method is used, and white OLEDs are produced by vacuum deposition.

Organic EL display devices using the color filter method have the problem of low light-emitting efficiency in principle, but they also have the problem of high power consumption because high brightness is achieved by increasing the output of the white OLED. For this reason, there is a demand for technology that can reduce power consumption while maintaining brightness in color filter organic EL display devices.

As a prior art that solves such a problem, for example, Patent Document 1 discloses a technology that enables a low-temperature curing process that does not damage the white organic EL layer when forming a color filter on a white organic EL layer in a color filter type organic EL display device that has a color filter on a white organic EL light-emitting layer, and enables the formation of a color filter with a high color material concentration made of a thin layer that enables high color reproducibility.

JP 2019-153389 A

However, in this technology, the color filters are formed with a high concentration of color material, so the fluorescence emitted from the color material is absorbed inside the color filter and cannot be extracted to the outside. As a result, the fluorescence cannot be used to improve the brightness of the organic EL display device.

In view of the above circumstances, the present invention aims to provide a color filter type organic EL display device that can utilize the fluorescence emitted from the color material of the color filter to improve brightness.

As a means for solving the above problems, a first aspect of the present invention is an organic electroluminescence display device comprising, in this order, at least a white organic electroluminescence light-emitting layer, color filters forming red, green and blue pixels, and an intermediate layer provided at a position in contact with a surface of the color filter opposite to the white organic electroluminescence light-emitting layer 2,
the intermediate layer contains a color material of the same kind as a color material contained in at least one pixel of the color filter,
The organic electroluminescence display device is characterized in that the color material concentration of the intermediate layer is lower than the color material concentration of the color filter.

The second aspect is the organic electroluminescence display device according to the first aspect, characterized in that the color filter and the intermediate layer contain the same type of polymer.

The third aspect is a method for manufacturing an organic electroluminescent display device according to the first or second aspect, characterized in that the intermediate layer is formed by heating the color filter during the manufacturing process, causing the color material in the color filter to migrate toward the intermediate layer.

According to the organic electroluminescent display device of the present invention, an intermediate layer made of a transparent resin is provided adjacent to the color filter, and the color material in the color filter can migrate to the intermediate layer side at the heating temperature during the manufacturing process. Therefore, a part of the color material in the color filter migrates to the intermediate layer by a heating process such as a drying process in the manufacturing process of the color filter. As a result, fluorescence is emitted from the color material that has migrated to the intermediate layer by the light from the white organic electroluminescent light-emitting layer, and the fluorescence improves the brightness of the organic electroluminescent display device.

FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention.

<Organic EL display device>
The organic EL display device of the present invention will be described with reference to FIG.

The organic EL display device 10 of the present invention is an organic electroluminescence display device comprising, in this order, at least a white organic electroluminescence light-emitting layer 2 (hereinafter also referred to as a white organic EL light-emitting layer 2), color filters 3 forming red, green, and blue pixels, and an intermediate layer 4 provided adjacent to the color filters.
The organic EL display device 10 of the present invention is characterized in that the intermediate layer 4 is made of a transparent resin that allows the color material in the color filter 3 to migrate toward the intermediate layer 4 by heating during the manufacturing process of the color filter. The heating temperature is assumed to be, for example, 50° C. to 100° C.

The pixel 6 of the color filter 3 has a red subpixel R, a green subpixel G, and a blue subpixel B.

In the organic EL display device 10 of the present invention, each subpixel R, G, B of the color filter 3 is made of a thin layer with a high color material concentration as in the conventional case, but an intermediate layer 4 is provided at a position in contact with the surface of the color filter 3 opposite to the white organic electroluminescence light-emitting layer 2. This makes it possible to increase the brightness of each subpixel R, G, B. This is thought to be because a part of the color material in each subpixel R, G, B moves to the intermediate layer 4. When the color material that has moved to the intermediate layer 4 is irradiated with light from the white organic electroluminescence light-emitting layer 2, fluorescence is emitted. Since the color material concentration in the intermediate layer 4 is lower than the color material concentration in the color filter 3, the fluorescence can come out without being absorbed by the color material. This can contribute to improving the brightness.

(White organic EL light-emitting layer)
The white organic EL light-emitting layer 2 is made of a laminate in which a plurality of layers including an organic semiconductor light-emitting layer are laminated, and is a light-emitting layer made of a so-called organic light-emitting diode (OLED) that emits white light.

(Color Filter)
The color filter 3 is formed with pixels 6 each including at least a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B as a constituent unit.

The color filter 3 is usually produced by preparing a colored photosensitive composition of black, red, green, or blue, in which a coloring composition consisting of fine black, red, green, or blue pigments is uniformly dispersed in a photosensitive transparent resin, applying the composition to a substrate, drying the composition, and then patterning the composition by photolithography.

Specifically, first, a black matrix 7 (see FIG. 1) is formed on a substrate using a black photosensitive composition that serves as a reference pattern. The black matrix 7 forms partitioned areas for forming red, green, and blue sub-pixels R, G, and B. Next, colored layers, for example, of red, green, and blue colors are formed in sequence to form the color filter 3.

In the organic EL display device 10 shown in FIG. 1, the above substrate is a white organic EL light-emitting layer 2 formed on a drive circuit board 1.

(Drive circuit board)
The driving circuit board 1 is a substrate in which a driving circuit for OLED is formed on the surface of a silicon wafer by, for example, processing the silicon wafer. The driving circuit for OLED is a current maintaining circuit. For example, when an image displayed by an organic EL display device is 30 frames per second, after one image is displayed, the next image is displayed 1/30 seconds later. That is, since the OLED, which is the light-emitting element of the organic EL display device, is a current-driven light-emitting element, it is necessary to maintain a current value required for emitting one image for 1/30 seconds. Since the liquid crystal element used in the liquid crystal display device is a voltage-driven type, one transistor is sufficient as a switching element, but at least two transistors are required for one subpixel in the organic EL display device.

(Middle class)
The intermediate layer 4 can be preferably made of a material obtained by removing coloring materials such as pigments and dyes from the composition of the color filter 3. Specifically, the coloring materials in the color filter 3 are removed from the intermediate layer 4 at a heating temperature of, for example, 50° C. to 100° C. in a drying step in the manufacturing process of the color filter 3.
It is necessary that the intermediate layer 4 is made of a transparent resin that can move toward the color filter 3. If the resin is the same, a stepwise difference in the color material concentration is formed at the interface where the color filter 3 and the intermediate layer 4 are joined. If there is such a difference in concentration, the fine particle color material is in a state where it is easily thermally diffused, so that a part of the color material can move to the intermediate layer 4 side where the color material is not present, for example, by heating at 50°C to 100°C. When the color material moves to the intermediate layer side to a certain extent and the color material concentration increases, the color material does not move any further, but the color material concentration in the region of the intermediate layer 4 close to the interface with the color filter 3 is lower than the color material concentration in the color filter 3. In other words, the color material concentration of the intermediate layer 4 is lower than the color material concentration of the color filter 3. Therefore, the fluorescence emitted from the color material can come out to the outside without being absorbed by the color material.

It is also possible to use a resin material that has a high affinity with the pigment in the coloring composition used in the color filter 3.

As shown in FIG. 1, the intermediate layer 4 is formed to cover the entire surface of the color filter 3, thereby improving the luminance of the entire color filter. On the other hand, depending on the pigment used in the color filter 3, the luminance may be lower than that of the other subpixels, and the luminance intensity of each color may not be balanced. When the objective is to improve the luminance of at least one of the subpixels R, G, and B, it is preferable to form the intermediate layer 4 only on the corresponding subpixel. In this case, the intermediate layer 4 may be disposed only on the subpixels of a single color, or may be disposed on the subpixels of any multiple colors.

For example, FIG. 2 is an example of an organic EL display device 10-1 in which an intermediate layer 4-1 is formed only on subpixel R. FIG. 3 is an example of an organic EL display device 10-2 in which an intermediate layer 4-2 is formed only on subpixel G. FIG. 4 is an example of an organic EL display device 10-3 in which an intermediate layer 4-3 is formed only on subpixel B. FIG. 5 is an example of an organic EL display device 10-4 in which an intermediate layer 4-4 is formed on subpixels R and G. FIG. 6 is an example of an organic EL display device 10-5 in which an intermediate layer 4-5 is formed on subpixels G and B. When forming an intermediate layer 4 on a plurality of adjacent subpixels as in FIG. 5 and FIG. 6, the intermediate layer 4 may be formed independently so as to correspond to each subpixel as in FIG. 5 and FIG. 6, or the intermediate layer 4 may be formed continuously between the subpixels without interruption. By forming the intermediate layer 4 independently so as to correspond to each subpixel, the color material concentration entering the intermediate layer 4 can be adjusted for each subpixel, making it easier to balance the emission intensity of each color. On the other hand, if the intermediate layer 4 is formed continuously between the subpixels without interruption, it becomes easier to form the intermediate layer 4 during manufacturing.

(Overcoat Layer)
The overcoat layer 5 serves to protect the color filter 3 and to flatten the surface.
The overcoat layer 5 is generally formed using a thermosetting or photosetting resin composition such as an acrylic resin, an epoxy resin, or a polyimide resin, but in the present invention, a thermosetting resin having excellent smoothness is used as the overcoat layer 5. For this overcoat layer 5, a resin material that is smooth and strong, has transparency, has high heat resistance and light resistance so that it does not yellow or whiten over a long period of time, and has excellent water resistance, solvent resistance, acid resistance, and alkali resistance can be suitably used.

Next, an embodiment of the present invention will be described.
Example 1
(Formation of Organic EL Light Emitting Layer)
A silicon wafer on which a drive circuit for an organic EL element was formed was used to form a white organic EL element by a vapor deposition method on the side of the silicon wafer on which the drive circuit was formed. Finally, a passivation layer made of silicon nitride was formed by a plasma CVD (Chemical Vapor Deposition) method, and the element was sealed to produce a substrate on which an organic EL light-emitting layer was formed.

(Preparation of material for forming color filter)
Next, materials for a color filter to be formed on the substrate on which the organic EL light-emitting layer was formed were prepared.

(1) Pigment for Black Resin Composition and Black Colored Composition The following colorants (pigments) were used in the colored resin composition.
Blue pigment: C.I. Pigment Blue 15:6
("LIONOL BLUE ES" manufactured by Toyo Color Co., Ltd.
Purple pigment: C.I. Pigment violet 23
("LIONOGEN VIOLET RL" manufactured by Toyo Color Co., Ltd.)
Yellow face: C.I. Pigment Yellow 139
(BASF Blue "Paliotol Yellow 2146HD"

Preparation of Black Colored Composition A black colored resin composition was prepared using each pigment.
The mixture of the following composition was stirred and mixed uniformly, then dispersed in a sand mill using glass beads having a diameter of 1 mm for 5 hours, and then filtered through a 5 μm filter to prepare a dispersion of a black pigment.
Blue pigment: C.I. Pigment Blue 15:6 11 parts by weight Purple pigment: C.I. Pigment violet 23 11 parts by weight Yellow face: C.I. Pigment Yellow 139 6 parts by weight Acrylic varnish (solid content 20%) 170 parts by weight

Then, the mixture of the following composition was stirred and mixed until it was homogenous, and then filtered through a 5 μm filter to obtain a black colored material (BLK-1).

A black photosensitive coloring composition (black photosensitive resin composition) was prepared using the above-mentioned coloring materials according to the composition shown in Table 1 (BLK-1).

(2) Red coloring composition Pigment for red coloring composition Red pigment: C.I. Pigment Red 254
(BASF "Ilgarfor Red B-CF")
Yellow pigment: C.I. Yellow 139
(BASF "Palioto Yellow L 2146HD")

Preparation of Red Colored Composition A mixture having the following composition was stirred and mixed uniformly, dispersed in a sand mill using glass beads having a diameter of 1 mm, and then filtered through a 5 μm filter to prepare a dispersion of a red pigment.
Red pigment: C.I. Pigment Red 254 78 parts by weight Yellow pigment: C.I. Pigment Yellow 139 22 parts by weight Acrylic varnish (solid content 20%) 215 parts by weight Thereafter, the mixture of the following composition was stirred and mixed to be uniform, and then filtered through a 5 μm filter to obtain a red colored composition (R-1).
Using the above-mentioned coloring materials, a blue photosensitive coloring composition was prepared according to the composition shown in Table 1 (RR-1).

(3) Green coloring composition Pigment for green coloring composition Green pigment: C.I. Pigment Green 58
(DIC "FASTOGEN GREEN A110"
Yellow pigment: C.I. Pigment Yellow 185
(BASF "Paliotol Yellow L 1155"

Preparation of Green Colored Composition A green colored resin composition was prepared using each pigment.
Green pigment: C.I. Pigment Green 58 65 parts by weight Yellow pigment: C.I. Pigment Yellow 185 35 parts by weight Acrylic varnish (solid content 20%) 215 parts by weight Then, the mixture of the following composition was stirred and mixed to be uniform, and then filtered through a 5 μm filter to obtain a green colored composition (G-1).
Using the above-mentioned coloring composition, a blue photosensitive coloring composition was prepared according to the formulation shown in Table 1 (GR-1).

(4) Blue coloring composition Pigment for blue coloring composition Blue pigment: C.I. Pigment Blue 15:6
("LIONOL BLUE ES" manufactured by Toyo Color Co., Ltd.)
Purple pigment: C.I. Pigment Violet 23
("LIONOGEN VIOLET RL" manufactured by Toyo Color Co., Ltd.)

Preparation of Blue Colored Composition A blue colored resin composition was prepared using each pigment.
Blue pigment: C.I. Pigment Blue 15:6 63 parts by weight Purple pigment: C.I. Pigment Violet 23 37 parts by weight Acrylic varnish (solid content 20%) 215 parts by weight Then, the mixture of the following composition was stirred and mixed to be uniform, and then filtered through a 5 μm filter to obtain a blue colored composition (B-1).
Using the above-mentioned coloring materials, a blue photosensitive coloring composition was prepared according to the composition shown in Table 1 (BR-1).

(5) Transparent Resin Composition Preparation of Transparent Resin Composition Transparent resin compositions were prepared according to the formulation shown in Table 2.

(Fabrication of Color Filter and Organic EL Display Device)
First, a transparent resin composition for a planarizing film was applied onto the organic EL light-emitting layer using a spinner so that the film thickness after curing was 0.1 μm. Then, the film was cured by heating at 100° C. for 10 minutes using a heating oven, completing the formation of a planarizing film.

Next, a black photosensitive resin composition was applied onto the flattening film using a spinner so that the film thickness of the cured finished product was 1.0 μm, and the composition was exposed to ultraviolet light through a pattern mask, developed with an alkali, washed with water, and dried to provisionally form a black matrix of a color filter having a pixel size of 2.4 μm × 2.4 μm. The composition was then heated in a heating oven at 80° C. for 10 minutes for curing, completing the formation of the black matrix.

Next, a green photosensitive resin composition was applied to the substrate on which the black matrix was formed using a spinner so that the film thickness of the cured finished product was 1.0 μm. The composition was then exposed to ultraviolet light through a pattern mask, developed with an alkali, washed with water, and dried to provisionally form a green layer (G) of a color filter with a pixel size of 2.4 μm x 2.4 μm. The composition was then heated in a heating oven at 80°C for 10 minutes to cure, completing the formation of the green layer (G) of the color filter.

Next, in the same manner as in the method for forming the green layer (G) of the color filter described above, a red photosensitive resin composition was applied with a spinner so that the film thickness of the cured finished product would be 1.0 μm, and the red layer (R) of the color filter with a pixel size of 2.4 μm x 2.4 μm was provisionally formed through a pattern mask through ultraviolet light exposure, alkaline development, water washing and drying processes. After that, it was heated in a heating oven at 80°C for 10 minutes to cure, and the formation of the red layer (R) of the color filter was completed.

Furthermore, in the same manner as in the above-mentioned method for forming the green layer (G) of the color filter, a blue photosensitive resin composition was applied with a spinner so that the film thickness of the cured finished product would be 1.0 μm, and the blue layer (B) of the color filter with a pixel size of 2.4 μm x 2.4 μm was provisionally formed through a pattern mask, UV exposure, alkaline development, water washing and drying processes. After that, it was heated in a heating oven at 80°C for 10 minutes for curing, and the formation of the blue layer (B) of the color filter was completed, and the color filter was produced.

After the color filter was formed, transparent resin composition OC-1 was applied with a spinner so that the finished film thickness would be 1 μm, and the red pixels were exposed to ultraviolet light, developed with an alkali, washed with water, and dried, and then heated in a heating oven at 80°C for 10 minutes to harden, forming overcoat layer 1 on the red pixels. Transparent resin composition OC-2 was then applied with a spinner so that the finished film thickness would be 1 μm, and the green and blue pixels were exposed to ultraviolet light, developed with an alkali, washed with water, and dried, and then heated in a heating oven at 80°C for 10 minutes to harden, forming overcoat layer 2 on the green and blue pixels.

After forming the overcoat layer 2, it was attached to a cover glass using a sealant Structbond XMF-T107 (manufactured by Mitsui Chemicals, Inc.) to prepare an organic EL display device.
Incidentally, overcoat layer 1 and overcoat layer 2 correspond to intermediate layer 4 and overcoat layer 5, respectively, in FIG.

Example 2
As in Example 1, after forming the color filter and overcoat layers 1 and 2, a microlens material was applied using a spinner so that the cured finished film thickness would be 2.4 μm, the entire coating was exposed to ultraviolet light, and then cured by heating at 80° C. for 10 minutes in a heating oven to form a microlens layer, and then an etch-back method was used to form lenses with a planarization film thickness of 1.2 μm and a lens height of 1.2 μm on the aforementioned red, green, and blue pixels.

After forming the microlenses, they were attached to a cover glass using the sealant Structbond XMF-T107 (Mitsui Chemicals) to create an organic EL display device.

Example 3
An organic EL display device was produced in the same manner as in Example 1, except that overcoat layer 1 was formed on blue pixels and overcoat layer 2 was formed on red and green pixels.

<Comparative Example 1>
An organic EL display device was produced in the same manner as in Example 1, except that the overcoat layer 1 was not used and the overcoat layer 2 was formed on the red, blue and green pixels.

<Comparative Example 2>
Only the overcoat layer 2 was formed in the same manner as in Comparative Example 1, and then a microlens was formed in the same manner as in Example 2 to fabricate an organic EL display device.

<Brightness evaluation>
The organic EL display devices fabricated in Examples 1 to 3 and Comparative Examples 1 and 2 were turned on, and a relative comparison of the luminance was made.
The luminance was measured using a CS-1000A manufactured by Konica Minolta.

The relative brightness calculated from the brightness measurement results is shown in Tables 3 and 4. In Tables 3 and 4, the brightness of Comparative Example 1 and Comparative Example 2 was set to 100%, respectively. The results show that Examples 1 and 2, which do not form microlenses, have relatively improved brightness compared to Comparative Example 1, which does not form an intermediate layer. Similarly, when comparing Example 3 and Comparative Example 2, which are equipped with microlenses, it was found that the brightness was relatively improved when an intermediate layer was formed.

1: Drive circuit board 2: White organic EL light-emitting layer 3: Color filter 4, 4-1, 4-2, 4-3, 4-4, 4-5: Intermediate layer 5: Overcoat layer 6: Pixel 7: Black matrix 10, 10-1, 10-2, 10-3, 10-4, 10-5: Organic EL display device R: Red subpixel G: Green subpixel B: Blue subpixel

Claims (4)

An organic electroluminescence display device comprising, in this order, at least a white organic electroluminescence light-emitting layer, a color filter having red pixels, green pixels, and blue pixels, and an intermediate layer formed at a position in contact with a surface of the color filter opposite to the white organic electroluminescence light-emitting layer,
a region of the intermediate layer in contact with the pixel contains the same type of color material as the color material contained in the pixel;
13. An organic electroluminescence display device, wherein a coloring material concentration of the intermediate layer in contact with the pixel is lower than a coloring material concentration of the pixel. 2. The organic electroluminescent display device according to claim 1, wherein in a junction region between the intermediate layer and the pixel, the intermediate layer and the pixel have a stepped concentration difference in color material concentration, and in a region other than the junction region of the pixel, the pixel has a color material uniformly dispersed therein. The organic electroluminescence display device according to claim 1 or 2, characterized in that the color filter and the intermediate layer contain the same type of polymer. The method for manufacturing an organic electroluminescent display device according to any one of claims 1 to 3, characterized in that the intermediate layer is formed by heating the color filter during the manufacturing process, causing the color material in the color filter to migrate toward the intermediate layer.

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